Acid zinc electroplating

ABSTRACT

Brightening additives for acid zinc electroplating baths and processes are provided. The additive is an acrylate selected from the group consisting of (1) an acrylate monomer of the general formula: WHEREIN R is methyl or hydrogen, R&#39;&#39; is alkyl of one to four carbon atoms, N IS A POSITIVE WHOLE INTEGER OF 1 TO 3, INCLUSIVE, R&#39;&#39;&#39;&#39; is alkyl of one to four carbon atoms, -CH2CH CH2, -CH2C*CH, -CH2COOCH3, -CH2COOC2H5, -CH2COR where R is as defined above, CH2CONH2, -CH2CN, -CH2CH2OH, -CH2CH2COO or -CH2CH2CH2SO3 , and X is CH3SO4 , C2H5SO4 , halide or is absent when R&#39;&#39;&#39;&#39; is CH2CH2COO or -CH2CH2CH2SO3 ; (2) a homopolymer of said acrylate monomer and (3) a copolymer of said acrylate monomer with at least one ethylenically unsaturated monomer selected from the group consisting of an Alpha , Beta -ethylenically unsaturated monocarboxylic acid, and alkyl ester of said acid wherein the alkyl group is from one to four carbon atoms, acrylonitrile, acrylamide, methacrylamide, vinyl acetate, vinyl sulfone and vinyl pyridine, the molar ratio of said acrylate monomer to said vinyl monomer being within the range of 0.9:0.1 to 0.1:0.9.

United States Patent 1 Rushmere 1 Mar. 27, 1973 [54] ACID ZINC ELECTROPLATING [75] Inventor: John Derek Rushmere, Wilmington,

Del.

[73] Assignee: E. I. du Pont de Nemours and Company, Wilmington, Del.

[22] Filed: Feb. 15, 1972 [21-] Appl. No.2 226,542

[52] US. Cl. ..204/55 R, 204/DIG. 2 [51] Int. Cl. ..C23b 5/12, C23b 5/46 [58] Field of Search ..204/55 R, 55 Y, 43, 44, 114

204/DIG. 2; 106/1; 117/130 E [56] References Cited UNITED STATES PATENTS 2,798,040 7/1957 Pye et al. ..204/55 R FOREIGN PATENTS OR APPLICATIONS 759,424 5/1967 Canada ..204/55 R Primary Examiner-G. L. Kaplan Att0rney-Robert W. Black [57] ABSTRACT Brightening additives for acid zinc electroplating baths and processes are provided. The additive is an acrylate selected from the group consisting of (1) an acrylate monomer of the general formula:

wherein R is methyl or hydrogen, R is alkyl of one to four carbon atoms, n is a positive whole integer of l to 3, inclusive, R" is alkyl of one to four carbon atoms, CH CH=CH ,CI-I2C CH, --CH COOCH CI-I COOC DV5, -CI-I COR where R is as 20 Claims, No Drawings- ACID ZINC ELECTROPLATING BACKGROUND OF THE INVENTION 1 Field of the Invention This invention relates to acid zinc electroplating baths and processes.

2. Prior Art The plating of zinc from acid baths is old and has long been practiced where the appearance of the deposited zinc is not especially important as in the coating of steel strip and conduit. Numerous patents concerning additives useful for improving the appearance of these deposits have issued over the years. Many of these have been directed to the use of sulfur and nitrogen compounds such as thioureas, pyridine (US. Pat. No. 2,355,505, issued to John L. Bray and Robert E. Howard on Aug. 8, 1944), sulfonated heterocyclics (US. Pat. No. 2,543,545, issued to Charles L. Faust and Arthur E. Bearse on Feb. 27, 1951), and alkylamines and polyamines (as disclosed in German Pat. No. 1910466, Sept. 17, 1970). A recent patent, US. Pat. No. 3,537,959 issued to Joachin Korpium and Hans J. Steeg, is directed to the use of primary amines and naphthalene sulfonic acid-formaldehyde condensation products for the production of bright zinc from acid baths. In my US. Pat. application Ser. No. 157,662 filed June 28, 1971, certain quaternary pyridinium compounds useful for this purpose are also disclosed.

SUMMARY OF THE INVENTION According to the present invention there is provided an aqueous acid zinc electroplating bath comprising an aqueous solution of a zinc salt maintained at a pH in the range of about 2.5 to 5.5 and having dissolved therein in an amount to give a bright zinc deposit an acrylate selected from the group consisting of (1) an acrylate monomer of the general formula:

wherein R is methyl or hydrogen, R is alkyl of one to four carbon atoms, n is a positive whole integer of l to 3, inclusive,

. R is alkyl of one to four carbon atoms, CH CH= CH CH C E CH, CH COOCH CH COOC CH COR where R is as defined above, CH CONH -CH CN, --CH CH OH,

Or CH2CH2CH2SO3 and X is CH SO C I-I SO halide or is absent when (2) a homopolymer of said acrylate monomer and (3) a copolymer of said acrylate monomer with at least one ethylenically unsaturated monomer selected from the group consisting of an a, ,B-ethylenically unsaturated monocarboxylic acid, an alkyl ester of said acid wherein the alkyl group is from one to four carbon atoms, acrylonitrile, acrylamide, methacrylamide, vinyl acetate, vinyl sulfone and vinyl pyridine, the molar ratio of said acrylate monomer to said vinyl monomer being within the range of 0.9:0. 1 to 0. 1:09.

There is also provided a process of electroplating bright zinc from the aforesaid electroplating bath.

DETAILED DESCRIPTION OF THE INVENTION Generally, the invention pertains to the elec trodeposition of zinc from acid zinc plating baths known to those skilled in the art. These baths can be formed by the dissolution of zinc oxide in non-complexing acids such as sulfuric or sulfarnic. The pH of the baths is adjusted to an operating range between about 2.5 and 5.5, preferably between 3.5 and 4.5, by the addition of aqueous ammonia and ammonium salts. Alternatively, the baths can be formed by thedissolution of commercial zinc and ammonium salts, such as the sulfates, in water with subsequent adjustment of the pH to a desired level in the normal operating range by means of aqueous ammonia, other alkali metal base or acid as required. Most commonly, baths based on zinc sulfate are used. While high chloride baths are to be avoided-generally any such commercial bath will have a pH greater than 5.5a small amount of chloride ions (up to 2 g./l.) in sulfate baths can be tolerated and in some cases may be beneficial. Temperature of operation is normally between 15C. and 45C. and is usually between 20C. and 30C. Mixtures of zinc salts, e.g., zinc sulfate and zinc sulfamate, can be used if desired. Also, other metal salts such as sodium sulfamate or potassium sulfate may be added to enhance electrical conductivity.

The zinc electrodeposits obtained from the acid sulfate baths, for example, are typically coarse and dull gray in appearance and have little commercial value, especially in the decorative plating of screws, chain, and other items of hardware. However, it has now been found that when certain quaternized dialkylaminoalkylacrylate monomers and more particularly homopolymers of quaternized dialkylaminoalkylacrylates or copolymers with other ethylenically unsaturated monomers are added to the acid zinc baths of the type described above in amounts from 0.05 to 5 g./l., preferably 0.1 to 1 g/l. a distinct improvement in the quality of the zinc electroplate results. In general, the monomers have the least effect showing only a smoothing action. The homopolymers impart brightness and shine to the deposits while the copolymers have been found to produce zinc deposits of commercially acceptable quality. Generally, excellent throwing power is also obtained from baths using such copolymers as is demonstrated by uniform coverage between the threads and in the head recesses of ordinary wood screws during barrel plating.

The quaternized dialkylaminoalkylacrylates useful in this invention have the general formula:

R is alkyl of one to four carbon atoms,

n is a positive whole integer of l to 3, inclusive, 1

R" is alkyl of l to 4 carbon atoms, --CH CH=CH CH,C CH, CH COOCH Cl-I COOC H -CH COR where R is as defined above, CH CONI-I CH CN, CH Cl-I OH, -CI-I CI-I COO or CH CH CH SO and Xis CH SO CH H SO halide or is absent when R" is --CH CH COO' or CH CH CH SO One monomer falling under this general description which has been found to be particularly useful as an additive is:

Z-methacryloxyethyl, dimethyl, 3-sulfopropyl ammonium betaine which may be prepared by the addition of propane sulfone to dimethylaminoethylmethacrylate.

This monomer may be readily polymerized in aqueous solution under the action of a peroxide initiator and mild temperature (6080C.) to give a homopolymer which shows similar plating characteristics to the monomer but which has the additional benefit that only one-third to one-tenth the amount of polymer is required to produce equivalent electroplate to that obtained from the monomer.

A still further improvement in plating performance (in the production of bright, shiny plate) is obtained by the use of copolymers of quaternized dialkylaminoalkylacrylates with other ethylenically unsaturated monomers such as an a, B-ethylenically unsaturated monocarboxylic acid such as acrylic acid or methacrylic acid, an alkyl ester of said acid wherein the alkyl group is from one to four carbon atoms, methacrylamide, acrylamide, acrylonitrile, vinyl acetate, vinyl sulfone and vinyl pyridine. Such copolymers usually have an additional advantage in that the ductility of the deposit is frequently markedly improved, i.e., brittleness is avoided. Of particular utility in this capacity is the copolymer formed between:

2-methacryloxyethyl trimethyl ammonium methyl sulfate and methacrylic acid This copolymer has been found to be very effective in producing bright, shiny zinc from acid sulfate baths with mole ratios of n/m varying between 0.9/0.1 to 0.1/0.9, preferably between 0.7/0.3 to 0.3/0.7, although maximum ductility is obtained and brittleness avoided at ratios of n/m about 0.3/0.7.

Other monomers'which have been found to have utility within the scope of this invention particularly when used as either homoor copolymers are the following:

Z-methacryloxyethyl, allyl, dimethyl ammonium bromide Z-methacryloxyethyl, propargyl, dimethyl ammonium bromide Z-methacryloxyethyl, cyanomethyl, dimethyl ammonium chloride 2-methacryloxyethyl, carboxamidomethyl, dimethyl ammonium chloride Z-methacryloxyethyl, carbomethoxy dimethyl ammonium chloride -2-methacryloxyethyl, 2-carboxyethyl, dimethyl ammonium betaine 2-acryloxyethyl, diethyl, methyl ammonium methyl sulfate methyl,

2-acryloxyethyl, diethyl, hydroxyethyl ammonium chloride 2-acryloxyethyl, diethyl, acetonyl ammonium chloride 2-acryloxyethyl, dimethyl, sec-butyl ammonium iodide.

Many equivalents not disclosed herein will be readily apparent to one skilled in the art. Thus, some benefits would be expected for the copolymers of the quaternized dialkylaminoalkylacrylates. with any other copolymerizable ethylenically unsaturated monomer. Further, the invention includes terpolymers, tetrapolymers and other copolymers.

In the examples which follow, the following electroplating bath was used unless otherwise indicated:

ZnSO, 140 g./l.

Temp. 25C.

The invention can be further understood by referring to the following examples in which parts and percentages are by weight unless otherwise indicated:

EXAMPLE 1 Z-Methacryloxyethyl, dimethyl, 3-sulfopropyl ammonium betaine (A) was prepared by adding 31 g. (0.25 mole) of propane sulfone to 39.3 g. (0.25 mole) dimethylaminoethylmethacrylate in 200 g. benzene solution. After standing overnight at room temperature, white crystals of A were obtained. Calc.: C- 47.3%, H7.52%, N5.0%; Found: C46.8%,H 7.61%, N4.99%.

Thirty g. of No. 6 X% inch wood screws were plated in a mini-barrel at 1.5 amps for 20 minutes using the acid zinc bath containing 2 g./l. of A. After a brief dip in a 0.1 percent solution of nitric acid, the screws were found to be bright and of commercially acceptable quality.

EXAMPLE 2 Z-Methacryloxyethyl, dimethyl, 3-sulfopropyl ammonium betaine (A) was polymerized by heating in a stirred vessel at 60C., 7.5 g. A, 35 g. water and 0.02 g. potassium persulfate for a period of 1 hour. The whole mix was then diluted to g. to give a 10 percent solution of poly A.

In a barrel plating test of 30 g. of No. 6 X 1% inch wood screws plated at 1.5 amps for 20 minutes in the acid zinc bath, only 0.8 g./l. poly A was required to give screws of similar quality to those obtained from Example 1.

EXAMPLE 3 Three g. (0.01 mol) 2-methacryloxyethyl, dimethyl, 3-sulfopropyl ammonium betaine, 0.75 g. (0.01 mol) methacrylic acid, 30 g. water and 0.04 g. potassium persulfate were heated at C. for 1 hour to give a slightly viscous product. Added at the rate of 20 ml./l. of acid zinc plating bath, this product performed as an excellent low current density brightener in the barrel plating of screws.

EXAMPLE 4 Z-Methacryloxyethyl, dimethyl carbomethoxymethyl ammonium chloride (B) was prepared as white crystals by adding 13 g. methyl chloroacetate to 8 g. dimethylaminoethylmethacrylate in acetone and standing at room temperature for 24 hours. The white crystals contained: C--49.70%, I-17.60%, N--5.27%. Theory: C49.82%, H7.55%, N5.28%.

Poly B was prepared by heating at 80C. for 1 hour, 5 g. B, g. water, 0.05 g. potassium persulfate. The clear viscous solution was poured into acetone to precipitate poly B as a white rubbery polymer. After drying under vacuum at 60C. it became brittle and was easily soluble in water.

Thirty g. No. 6 X '79 inch wood screws were barrel plated at 1.5 amps for 20 minutes in the zinc sulfate bath containing 0.2 g./l. poly B. The screws were bright and shiny and were further improved in appearance by a short dip in a 0.1 percent solution of nitric acid. The zinc deposit was slightly brittle as evidenced by the spalling off of a few small flecks of zinc upon shaking the screws.

EXAMPLE 5 2-Methacryloxyethyl; dimethyl cyanomethyl ammonium chloride (C) was prepared as white crystals by adding 8 g. of chloroacetonitrile to 8 g. of dimethylaminoethylmethacrylate in 16 g. of methyl ethyl ketone. The product crystallized out on standing overnight. It contained: 51.55% C, 7.34% H, 12.12%N. Theory: 51.75% C, 7.34% H, 12.07% N.

Poly C was prepared in a similar manner to the poly B of Example 4. In the barrel plating of screws it was found to also behave similarly.

EXAMPLE 6 2-Methacryloxyethyl, dimethyl carboxamidomethyl ammonium chloride (D) was prepared by standing together 9.4 g. of chloroacetamide and 8 g. of dimethylaminoethylmethacrylate in g. of dimethyl formamide for 12 days. After this time, a few white solids had appeared. Upon pouring the solution into methyl ethyl ketone considerable white crystalline solids precipitated. They contained: Cl13.92%. Theory for Cl: 14.18%.

Poly D was prepared by polymerizing D in aqueous solution under the action of potassium persulfate as an initiator following the practice of Example 4. Poly D was found to be an effective additive for the barrel plating of screws.

EXAMPLE 7 Z-Methacryloxyethyl, dimethyl propargyl ammonium bromide (E) was prepared by adding 8 g. of propargyl bromide to 12 g. of dimethylaminoethylmethacrylate in 20 g. of methyl ethyl ketone. The white crystals formed analyzed as C-47.88%, l-l6.58%, N5.l3%. Theory: C-47.85%, 1-l6.52%, N5.07%. Poly E, prepared following the teachings of the foregoing examples was found to be an effective brightener for acid zinc electroplating.

EXAMPLES s-13 A. series of copolymers of 2-methacryloxyethyl trimethyl ammonium methyl sulfate (X) with methacrylic acid (Y) in mol. ratios of X/Y varying between 0.9/0.1 and 0.1 to 0.9 were prepared by polymerizing the monomers in aqueous solution at C., using potassium persulfate as catalyst. The copolymers were precipitated in acetone and dried under vacuum at 60C. to give brittle colorless solids easily soluble in water. Composition was found by microanalysis as shown in Table 1.

TABLEI Z-Methacryloxyethyl trimethyl ammonium methylsulfate (X) methacrylic acid (Y) copolymers Ex. M015 M015 No. X Y C H N S LV. 8 0.10 0.90 51.41 7.65 1.29 3.03 9 0.30 0.70 47.71 7.50 2.77 1.71 10 0.48 0.52 45.24 7.21 3.70 3.05 11 0.47 0.53 46.15 6.76 3.68 2.02 12 0.70 0.30 43.40 7.15 4.27 2.61 13 0.86 0.14 42.36 7.77 4.72 10.55

l.V. intrinsic viscosity (by flow viscosimeter) These polymers were all found to be excellent additives for producing bright, shiny zinc from the acid sulfate bath when added in amounts of from 0.05 to 0.5 g./l. It was also found that the ductility of deposits was greatly improved using polymers containing a greater mole percentage of methacrylic acid. The polymer of Example 9 was found to combine the optimums ofbrightness, shine and ductility.

Molecular weight of the polymer was found to have little effect on its behavior as an additive. The products from Examples 10 and l l were closely similar.

EXAMPLES 14-19 Listed in Table 11 are further examples of copolymers of quaternized dialkylaminoacrylates with other ethylenically unsaturated monomers which have been found useful as additives in acid zinc plating when added in amounts of from 0.05 to 0.5 g./l. These copolymers were all prepared in aqueous solution using the teachings of foregoing examples.

TABLE II Polyacrylates in acid zinc plating Mole ratio in polymerization mix What is claimed is:

1. An aqueous acidzinc electroplating bath comprising an aqueous solution of a zinc salt maintained at a pH in the range of about 2.5 to 5.5 and having dissolved 7 8 therein in an amount to give a bright zinc deposit an 5. The acid electroplating bath of claim 2 wherein acrylate selected from the group consisting of (1) an the ethylenically unsaturated monomer is methacrylic acrylate monomer of the general formula: acid.

6. The acid electroplating bath of claim 2 wherein 5 the pH of the bath is within the range of about 3.5 to

I r n g 4.5 and the copolymer concentration 18 about 0.1 to l g./l. R 7. The acid electroplating bath of claim 1 wherein the acrylate is added to give a bath concentration wherein 1 within the range of about 0.05 to g./l. v

R is methyl or hydrogen, 8. The acid electroplating bath of claim 7 wherein R is alkyl of one to four carbon atoms, the P of the bath is within h range of about to n is a positive whole integer of 1 to 3 inclusive, and the acrylate concentratlon 1 i lk f one to f carbon atoms 9. The acid electroplating bath of claim 1 wherein CH2, 5 CH, CH2COOCH: the acrylate isan acrylate monomer of the general forcn cooc CH COR where R is as defined above, CH CONH CH CN, CH CH OH, O CH CH COO or CH CH CH SO;, and H Xis CH3SO4 a C2H5SO4 halide or is absent when R" is CH CH COO' or CH CH CH SO R (2) a homopolymer of said acrylate monomer and (3) a copolymer of said acrylate monomer with at least one ethylenically unsaturated monomer selected from the whel:em

R 18 methyl or hydrogen,

group consisting of an a, ,B-ethylenically unsaturated monocarboxylic acid, an alkyl ester of said acid wherein the alkyl group is from one to four carbon atoms, acrylonitrile, acrylamide, methacrylamide, vinyl acetate, vinyl sulfone and vinyl pyridine, the molar ratio of said acrylate monomer to said unsaturated 3O monomer being within the range of O.9:O.l to 0.1:0.9.

2. The acid electroplating bath of claim 1 wherein the acrylate is a copolymer of an acrylate monomer of R is methyl or ethyl,

R" is alkyl of l to 4 carbon atoms, CH CH=CH -Cl-I C 5 CH, CH COOCH CH COOC H -CH COR where R is as defined above, CH CONH -CH CN, -CH CH OH, -CH CH COO- or -CH CH CH SO and Xis CH SO;, C2H5SOC halide or is absent when R" is Or CH2CH2CH2SO3 10. The acid electroplating bath of claim 9 wherein the general formula: the pH of the bath is within the range of about 3.5 to

4.5. if 11. The acid electroplating bath of claim 1 wherein f the acrylate is a homopolymer of an acrylate monomer R of the general formula:

' E I I! wherein 0H,=( OCnH2nN (R )2R X- R is methyl or hydrogen, R R is methyl or ethyl, wherein R" is alkyl of one to four carbon atoms, -CH CH R is methyl or hydrogen, 2 2 5 z s R is methyl or ethyl, z zs 2 Where R is as defined R" is alkyl of one to four carbon atoms, CH CH above, -CH C0NH CH CN, -CH CH OH, 3 c c]-1 E H, cH c00cH 2 2 2 2 2 :;Z and is CH COOC -CH COR where R is as defined CH SO H SO;, halide or is absent when R is b ve, -CH CONH CH CN, CH CH OH, 2 2 or 2 2 2 3' with at -CH CH COO' or CH CH CH SO and xis least one ethylenically unsaturated monomer (II-[ 50 l-1 80;, halid i ab t wh n Rf is selected from the group consisting of an a, B- CH CH COO' or CH CH CH SO ethylenically unsaturated monocarboxylic acid, an 12. The acid electroplating bath of claim 11 wherein alkyl ester of said acid wherein the alkyl group is the pH of the bath is within the range of about 3.5 to from one to four carbon atoms, acrylonitrile, 4.5.

acrylamide, methacrylamide, vinyl acetate, vinyl 13. In a process of electroplating bright zinc from an sulfone and vinyl pyridine, the copolymer having a aqueous acid zinc electroplating bath having a zinc salt molar ratio of said acrylate monomer to said undissolved therein the improvement comprising mainsaturated monomer being within the range of taining said bath at a pH in the range of about 2.5 to 5.5 0.7/0.3 to 0.3/0.7. and adding thereto in an amount efiective to give a 3. The acid electroplating bath of claim 2 wherein bright zinc deposit an acrylate selected from the group the copolymer is about 30 molar percent 2- consisting of (1) an acrylate monomer of the general methacryloxyethyl trimethyl ammonium methyl sulfate o ula: and about 70 molar percent methacrylic acid.

4. The acid electroplating bath of claim 3 wherein H the pH of the bath is within the range of about 3.5 to 4.5. R

wherein R is methyl or hydrogen,

R is alkyl of one to four carbon atoms,

n is a positive whole integer of l to 3 inclusive,

R" is alkyl of one to four carbon atoms, CH CH= CH CH C CH, --Cl-l COOCH Cl-l COOC -Cl-l COR where R is as defined above, CH CONH CH CN, --CH CH OH, -CH CH COO- or CH CH CH SO and X-is CH SOR- H SO halide or is absent from R is CH CH COO- or -CH CH CH SO (2) a homopolymer of said acrylate monomer and (3) a copolymer of said acrylate monomer with at least one ethylenically unsaturated monomer selected from the group consisting of an a, B-ethylenically unsaturated monocarboxylic acid, an alkyl ester of said acid wherein the alkyl group is from one to four carbon atoms, acrylonitrile, acrylamide, methacrylamide, vinyl acetate, vinyl sulfone and vinyl pyridine, the molar ratio of said acrylate monomer to said unsaturated monomer being within the range of 0.9201 to 0.1 :0.9.

14. The process of claim 13 wherein the acrylate is added to give a bath concentration within the range of about 0.05 to 5 g./l.

15. The process of claim 14 wherein the acrylate is added to give a bath concentration within the range of about 0.1 to l g./l., the pH is maintained within the range of about 3.5 to 4.5 and the bath is at a temperature in the range of 15 to 45C.

16. The process of claim 15 wherein the acrylate is a copolymer of an acrylate monomer of the general formula:

R is methyl or ethyl,

R" is alkyl of one to four carbon atoms, -CH CH CH CH CH CH, CH,COOCH CH COOC CH COR where R is as defined above, CH CONH -CH CN, CH CH 0H, --CH CH COO' or CH CH CH SO and X is CH SO H SO halide or is absent when R" is -CH CH COO- or -CH CH CH SO with at least one ethylenically unsaturated monomer selected from the group consisting of an a, B- ethylenically unsaturated monocarboxylic acid, an alkyl ester of said acid wherein the alkyl group is from one to four carbon atoms, acrylonitrile, acrylamide, methacrylamide, vinyl acetate, vinyl sulfone and vinyl pyridine, the copolymer having a molar ratio of said acrylate monomer to said unsaturated monomer within the range of 0.7/0.3 to 0.3/0.7 and the bath is at a temperature in the range of about 20 to 30C.

17. The process of claim 16 wherein the ethylenically unsaturated monomer ismethacrylic acid.

18. The process of claim 16 wherein the copolymer IS about 30 molar percent Z-methacryloxyethyl trimethyl ammonium methyl sulfate and about molar percent methacrylic acid.

19. The process of claim 15 wherein the acrylate is an acrylate monomer of the general formula:

wherein R is methyl or hydrogen,

R is methyl or ethyl,

R" is alkyl of one to four carbon atoms, CH CH= CH CH C E CH, CH COOCl-l CH COOC CH COR where R is as defined above, CH CONH -CH CN, CH CH OH, CH CI-l COO or -CH Cl-l CH SO and X-is CH, C H SO halide or is absent when R is CH,CH COO or CH,CH CH SO 20. The process of claim 15 wherein the acrylate is a homopolymer of an acrylate monomer of the general formula: 

2. The acid electroplating bath of claim 1 wherein the acrylate is a copolymer of an acrylate monomer of the general formula: wherein R is methyl or hydrogen, R'' is methyl or ethyl, R'''' is alkyl of one to four carbon atoms, -CH2CH CH2, -CH2CH * CH, -CH2COOCH3, -CH2COOC2H5, -CH2COR where R is as defined above, -CH2CONH2, -CH2CN, -CH2CH2OH, -CH2CH2COO or -CH2CH2CH2SO3 , and X is CH3SO4 , C2H5SO4 , halide or is absent when R'''' is -CH2CH2COO or -CH2CH2CH2SO3 with at least one ethylenically unsaturated monomer selected from the group consisting of an Alpha , Beta -ethylenically unsaturated monocarboxylic acid, an alkyl ester of said acid wherein the alkyl group is from one to four carbon atoms, acrylonitrile, acrylamide, methacrylamide, vinyl acetate, vinyl sulfone and vinyl pyridine, the copolymer having a molar ratio of said acrylate monomer to said unsaturated monomer being within the range of 0.7/0.3 to 0.3/0.7.
 3. The acid electroplating bath of claim 2 wherein the copolymer is about 30 molar percent 2-methacryloxyethyl trimethyl ammonium methyl sulfate and about 70 molar percent methacrylic acid.
 4. The acid electroplating bath of claim 3 wherein the pH of the bath is within the range of about 3.5 to 4.5.
 5. The acid electroplating bath of claim 2 wherein the ethylenically unsaturated monomer is methacrylic acid.
 6. The acid electroplating bath of claim 2 wherein the pH of the bath is within the range of about 3.5 to 4.5 and the copolymer concentration is aBout 0.1 to 1 g./l.
 7. The acid electroplating bath of claim 1 wherein the acrylate is added to give a bath concentration within the range of about 0.05 to 5 g./l.
 8. The acid electroplating bath of claim 7 wherein the pH of the bath is within the range of about 3.5 to 4.5 and the acrylate concentration is 0.1 to 1 g./l.
 9. The acid electroplating bath of claim 1 wherein the acrylate is an acrylate monomer of the general formula: wherein R is methyl or hydrogen, R'' is methyl or ethyl, R'''' is alkyl of 1 to 4 carbon atoms, -CH2CH CH2, -CH2C*CH, -CH2COOCH3, -CH2COOC2H5, -CH2COR where R is as defined above, -CH2CONH2, -CH2CN, -CH2CH2OH, -CH2CH2COO or -CH2CH2CH2SO3 , and X is CH3SO4 , C2H5SO4 , halide or is absent when R'''' is -CH2CH2COO or -CH2CH2CH2SO3 .
 10. The acid electroplating bath of claim 9 wherein the pH of the bath is within the range of about 3.5 to 4.5.
 11. The acid electroplating bath of claim 1 wherein the acrylate is a homopolymer of an acrylate monomer of the general formula: wherein R is methyl or hydrogen, R'' is methyl or ethyl, R'''' is alkyl of one to four carbon atoms, -CH2CH CH2, -CH2CH * CH, -CH2COOCH3, -CH2COOC2H5, -CH2COR where R is as defined above, -CH2CONH2, -CH2CN, -CH2CH2OH, -CH2CH2COO or -CH2CH2CH2SO3 , and X is CH3SO4 , C2H5SO4 , halide or is absent when R'''' is -CH2CH2COO or -CH2CH2CH2SO3 .
 12. The acid electroplating bath of claim 11 wherein the pH of the bath is within the range of about 3.5 to 4.5.
 13. In a process of electroplating bright zinc from an aqueous acid zinc electroplating bath having a zinc salt dissolved therein the improvement comprising maintaining said bath at a pH in the range of about 2.5 to 5.5 and adding thereto in an amount effective to give a bright zinc deposit an acrylate selected from the group consisting of (1) an acrylate monomer of the general formula: wherein R is methyl or hydrogen, R'' is alkyl of one to four carbon atoms, n is a positive whole integer of 1 to 3 inclusive, R'''' is alkyl of one to four carbon atoms, -CH2CH CH2, -CH2C*CH, -CH2COOCH3, -CH2COOC2H5, -CH2COR where R is as defined above, -CH2CONH2, -CH2CN, -CH2CH2OH, -CH2CH2COO or -CH2CH2CH2SO3 , and X is CH3SO4 , C2H5SO4 , halide or is absent from R'''' is -CH2CH2COO or -CH2CH2CH2SO3 ; (2) a homopolymer of said acrylate monomer and (3) a copolymer of said acrylate monomer with at least one ethylenically unsaturated monomer selected from the group consisting of an Alpha , Beta -ethylenically unsaturated monocarboxylic acid, an alkyl ester of said acid wherein the alkyl group is from one to four carbon atoms, acrylonitrile, acrylamide, methacrylamide, vinyl acetate, vinyl sulfone and vinyl pyridine, the molar ratio of said acrylate monomer to said unsaturated monomer being wIthin the range of 0.9:0.1 to 0.1:0.9.
 14. The process of claim 13 wherein the acrylate is added to give a bath concentration within the range of about 0.05 to 5 g./l.
 15. The process of claim 14 wherein the acrylate is added to give a bath concentration within the range of about 0.1 to 1 g./l., the pH is maintained within the range of about 3.5 to 4.5 and the bath is at a temperature in the range of 15* to 45*C.
 16. The process of claim 15 wherein the acrylate is a copolymer of an acrylate monomer of the general formula: wherein R is methyl or hydrogen, R'' is methyl or ethyl, R'''' is alkyl of one to four carbon atoms, -CH2CH CH2, -CH2CH * CH, -CH2COOCH3, -CH2COOC2H5, -CH2COR where R is as defined above, -CH2CONH2, -CH2CN, -CH2CH2OH, -CH2CH2COO or -CH2CH2CH2SO3 , and X is CH3SO4 , C2H5SO4 , halide or is absent when R'''' is -CH2CH2COO or -CH2CH2CH2SO3 with at least one ethylenically unsaturated monomer selected from the group consisting of an Alpha , Beta -ethylenically unsaturated monocarboxylic acid, an alkyl ester of said acid wherein the alkyl group is from one to four carbon atoms, acrylonitrile, acrylamide, methacrylamide, vinyl acetate, vinyl sulfone and vinyl pyridine, the copolymer having a molar ratio of said acrylate monomer to said unsaturated monomer within the range of 0.7/0.3 to 0.3/0.7 and the bath is at a temperature in the range of about 20* to 30*C.
 17. The process of claim 16 wherein the ethylenically unsaturated monomer is methacrylic acid.
 18. The process of claim 16 wherein the copolymer is about 30 molar percent 2-methacryloxyethyl trimethyl ammonium methyl sulfate and about 70 molar percent methacrylic acid.
 19. The process of claim 15 wherein the acrylate is an acrylate monomer of the general formula: wherein R is methyl or hydrogen, R'' is methyl or ethyl, R'''' is alkyl of one to four carbon atoms, -CH2CH CH2, -CH2C*CH, -CH2COOCH3, -CH2COOC2H5, -CH2COR where R is as defined above, -CH2CONH2, -CH2CN, -CH2CH2OH, -CH2CH2COO or -CH2CH2CH2SO3 , and X is CH3 SO4 , C2H5SO4 , halide or is absent when R'''' is -CH2CH2COO or -CH2CH2CH2SO3 .
 20. The process of claim 15 wherein the acrylate is a homopolymer of an acrylate monomer of the general formula: wherein R is methyl or hydrogen, R'' is methyl or ethyl, R'''' is alkyl of one to four carbon atoms, -CH2CH CH2, -CH2CH * CH, -CH2COOCH3, -CH2COOC2H5, -CH2COR where R is as defined above, -CH2CONH2, -CH2CN, -CH2CH2OH, -CH2CH2COO or -CH2CH2CH2SO3 , and X is CH3SO4 , C2H5SO4 , halide or is absent when R'''' is -CH2CH2COO or -CH2CH2CH2SO3 . 